Method and system for operating a heat pump of a vehicle

ABSTRACT

Methods and systems for providing control of a heat pump of a motor vehicle are presented. In one operating mode, speed of a heat pump compressor is controlled responsive to an outlet pressure of the heat pump compressor. In a second operating mode, speed of the heat pump compressor is controlled responsive to a pressure ratio between an inlet and an outlet of the heat pump compressor.

FIELD

The present description relates to methods and a system for providingclimate control for a vehicle. The methods and system may beparticularly useful for vehicles that are solely electrically propelledor vehicles that include hybrid powertrains.

BACKGROUND AND SUMMARY

A vehicle may include a heat pump to adjust environmental conditions ofa vehicle's passenger compartment. The heat pump may operate in severaldifferent modes to control the vehicle cabin environment. For example,the heat pump may be operated in a heating mode where thermal energy istransferred from the heat pump to coolant that warms the vehicle cabin.The heat pump may be operated in a cooling mode where a heat exchangerin the vehicle's cabin operates as an evaporator to cool air that passesover the interior heat exchanger. The heat pump may also operate in ade-humidification mode where the heat pump cools passenger cabin air toremove humidity and then warms the air to heat the passenger cabin ordefrost vehicle windows.

The ability to operate the heat pump in more than one mode increases theutility of the heat pump. However, operating the heat pump in more thanone mode may make controlling the heat pump more challenging. Inparticular, it may be possible for the heat pump's compressor to flowless refrigerant and lubricant during some operating conditions of theheat pump's different operating modes. For example, compressorlubrication may be reduced due to high pressure ratios across thecompressor when a heat pump is operated in a heating or dehumidificationmode where an exterior heat exchanger operates as an evaporator andcompressor inlet or suction pressure is driven by ambient temperature.The reduced flow of compressor lubricant may increase the possibility ofheat pump compressor degradation. Therefore, it may be desirable toprovide a way of operating the compressor in the different heat pumpmodes so that heat pump compressor lubrication may be ensured.

The inventors herein have recognized the above-mentioned disadvantageand have developed a vehicle system, comprising: a refrigerant loopincluding a compressor; a first pressure sensor; and a controllerincluding executable instructions stored in non-transitory memory toadjust a speed of the compressor in response to a pressure ratio acrossan outlet of the compressor and an inlet of the compressor, the pressureratio based at least in part on output of the first pressure sensor.

By controlling heat pump compressor speed in response to a pressureratio between a heat pump compressor inlet and a heat pump compressoroutlet, it may be possible to provide the technical result of reducingthe possibility of heat pump compressor degradation. In particular, thepossibility of heat pump compressor degradation may be reduced when theheat pump is operating in a heating mode or dehumidification mode whereheat pump compressor inlet pressure may vary substantially. If thepressure ratio between the heat pump compressor inlet and outletincreases beyond a threshold, compressor speed may be reduced toincrease refrigerant and lubrication flow through the compressor. Assuch, the possibility of compressor degradation may be reduced. If thepressure ratio increases sufficiently, the compressor may be stoppedbased on a recognition that compressor lubrication decreases asrefrigerant and lubricant flow through the heat pump compressordecreases at higher pressure ratios across the compressor.

The present description may provide several advantages. For example, theapproach may reduce the possibility of heat pump compressor degradation.Further, the approach may be provided without a significant increase insystem cost. Further still, the approach may be applied to a variety ofsystem configurations to provide similar functionality in a variety ofdifferent systems.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingan example of an example, referred to herein as the DetailedDescription, when taken alone or with reference to the drawings, where:

FIG. 1 is a schematic diagram of a vehicle;

FIGS. 2-4B show a vehicle climate control system for the vehicle of FIG.1 operating in different modes;

FIG. 5 shows a method for operating a heat pump of the type shown in thesystem of FIGS. 2-4B;

FIGS. 6-8 show different methods for inferring heat pump compressorinlet pressure for determining a pressure ratio across a vehicle heatpump compressor; and

FIG. 9 shows a method for adjusting speed of a heat pump compressor.

DETAILED DESCRIPTION

The present description is related to operating a heat pump compressorfor a climate control system of a vehicle. The vehicle climate controlsystem may be included in an electric or hybrid vehicle as is shown inFIG. 1. The vehicle climate control system may include a heat pump andoperating modes as described in FIGS. 2-4B. The heat pump may be may beoperating according to the methods of FIGS. 5-9 to reduce thepossibility of heat pump compressor degradation.

Referring to FIG. 1, a vehicle 10 including an engine 12, an electricalmachine 14, a first electrical energy storage device 11, and a secondelectrical energy storage device 220 is shown. In one example, thevehicle may be propelled solely via the engine 12, solely via theelectrical machine 14, or by both the engine 12 and the electricalmachine 14. The electrical machine may be supplied electrical power viathe second electrical energy storage device 220. The second electricalenergy storage device 220 may be recharged via engine 12 providing powerto electrical machine 14 and electrical machine outputting electricalenergy to second electric energy storage device 220. Alternatively,electrical energy storage device may be recharged via converting thevehicle's kinetic energy into electrical energy via electrical machine14 during vehicle deceleration or hill descent. Second electrical energystorage device 220 may also be recharged from a stationary power gridvia a home charging system or a remote charging system (e.g., a chargingstation). In one example, second electrical energy storage device 220 isa battery. Alternatively, second electrical energy storage device 220may be a capacitor or other storage device. First electrical energystorage device 11 may be a low voltage battery for cranking the engineand operating vehicle electrical consumers (e.g., lights).

Referring to FIG. 2, a schematic representation of a vehicle 10 with aclimate control system 24 is shown. Flow direction arrows (e.g., 204)describe refrigerant flow in climate control system 24 when climatecontrol system 24 is operated in a cooling mode. The vehicle 10 may haveany suitable drivetrain and may include an engine 12 that may be used topropel the vehicle 10 and/or power vehicle components. The vehicle 10may include a single engine 12 as shown in FIG. 1 and it may beconfigured as an internal combustion engine adapted to combust anysuitable type of fuel, such as gasoline, diesel fuel, or hydrogen. Asanother option, vehicle 10 may be configured as a hybrid vehicle thatmay have a plurality of power sources, such as a non-electrical powersource like an engine and an electrical power source as is shown inFIG. 1. The vehicle 10 may include a passenger compartment 20, an enginecompartment 22, and a climate control system 24.

Devices and fluidic passages or conduits are shown as solid lines inFIGS. 2-4B. Electrical connections are shown as dashed lines in FIGS.2-4B. In FIGS. 2-4B, coolant subsystem 30 is shown with an engine 12,but in some examples engine 12 may be omitted.

The passenger compartment 20 may be disposed inside the vehicle 10 andmay receive one or more occupants. A portion of the climate controlsystem 24 may be disposed in the passenger compartment 20.

The engine compartment 22 may be disposed proximate the passengercompartment 20. An engine 12 and/or an electric machine 14 as well as aportion of the climate control system 24 may be disposed in the enginecompartment 22. The engine compartment 22 may be separated from thepassenger compartment 20 by a bulkhead 26.

An outlet side 60B of compressor 60 is directly coupled to an inlet sideof intermediate heat exchanger 42 via a conduit. Controller 212 maysupply current and voltage to adjust a speed of compressor 60.Compressor 60 may pressurize and circulate the refrigerant through theheat pump subsystem 32. The compressor 60 may be powered by anelectrical power source. Speed of compressor 60 may be determined viasensor 299 which may be electrically coupled to controller 212.

Intermediate heat exchanger 42 may facilitate the transfer of thermalenergy between the coolant subsystem 30 and the heat pump subsystem 32.In particular, heat may be transferred from heat pump subsystem 32 tocoolant subsystem 30. The intermediate heat exchanger 42 may be part ofthe coolant subsystem 30 and the heat pump subsystem 32, and it mayfacilitate the transfer of thermal energy from heat pump subsystem 32 tocoolant subsystem 30 without mixing or exchanging the heat transferfluids in the coolant subsystem 30 and heat pump subsystems 32.

Intermediate heat exchanger 42 is shown directly coupled to an inletside of first control valve 262 and an inlet side of first expansiondevice 264, which may be a fixed area expansion device. The firstexpansion device 264 may be provided to change the pressure of therefrigerant. For instance, the first expansion device 264 may be a fixedarea expansion device or variable position valve that may or may not beexternally controlled. The first expansion device 264 may reduce thepressure of the refrigerant that passes through the first expansiondevice 264 from the intermediate heat exchanger 42 to the exterior heatexchanger 66. As such, high pressure refrigerant received from theintermediate heat exchanger 42 may exit the first expansion device 64 ata lower pressure and as a liquid and vapor mixture in a heating mode.

First control valve 262 may be selectively opened and closed viacontroller 212. When first control valve 262 is in an open position, itprovides a path of least fluidic resistance to exterior heat exchanger66 such that there is little pressure drop across fixed area expansiondevice 264. Outlet sides of fixed area expansion device 264 and firstcontrol valve 262 are shown directly coupled to an inlet side 66A ofexterior heat exchanger 66. An outlet side 66B of exterior heatexchanger 66 is shown directly coupled to a first inlet side 78A ofinternal heat exchanger 78 and coupled to an inlet side of accumulator72 via second control valve 222. The exterior heat exchanger 66 may bedisposed outside the passenger compartment 20. In a cooling mode or airconditioning context, the exterior heat exchanger 66 may function as acondenser and may transfer heat to the surrounding environment tocondense the refrigerant from a vapor to liquid. In a heating mode, theexterior heat exchanger 66 may function as an evaporator and maytransfer heat from the surrounding environment to the refrigerant,thereby causing the refrigerant to vaporize. A first outlet side 78B ofinternal heat exchanger 78 is directly coupled to inlets of secondexpansion device 74 and third expansion valve 274.

Internal heat exchanger 78, may transfer thermal energy betweenrefrigerant flowing through different regions of the heat pump subsystem32. Internal heat exchanger 78 may be disposed outside the passengercompartment 20. In a cooling mode or air conditioning context, heat maybe transferred from refrigerant that is routed from the exterior heatexchanger 66 to the interior heat exchanger 76 to refrigerant that isrouted from the accumulator 72 to the compressor 60. In the heatingmode, the internal heat exchanger 78 does not transfer thermal energybetween such refrigerant flow paths since the second expansion device 74is closed, thereby inhibiting the flow of refrigerant through a portionof the internal heat exchanger 78.

The second expansion device 74 may be disposed between and may be influid communication with the exterior heat exchanger 66 and the interiorheat exchanger 76. The second expansion device 74 may have a similarconfiguration as the first expansion device 264 and may be provided tochange the pressure of the refrigerant similar to the first expansiondevice 264. In addition, the second expansion device 74 may be closed toinhibit the flow of refrigerant. More specifically, the second expansiondevice 74 may be closed to inhibit the flow of refrigerant from theexterior heat exchanger 66 to the interior heat exchanger 76 in aheating mode.

An outlet side of second expansion device 74 is directly coupled to aninlet side of interior heat exchanger 76. And outlet side 76B ofinterior heat exchanger 76 is directly coupled to an inlet ofaccumulator 72. The interior heat exchanger 76 may be in fluidcommunication with the second expansion device 74. The interior heatexchanger 76 may be disposed inside the passenger compartment 20. In acooling mode or air conditioning context, the interior heat exchanger 76may function as an evaporator and may receive heat from air in thepassenger compartment 20 to vaporize the refrigerant. Refrigerantexiting the interior heat exchanger 76 is directly routed to theaccumulator 72. In the heating mode, refrigerant may not be routed tothe interior heat exchanger 76 due to the closure of the secondexpansion device 74.

An outlet of accumulator 72 is directly coupled to second inlet 78C ofinternal heat exchanger 78. The accumulator 72 may act as a reservoirfor storing any residual liquid refrigerant so that vapor refrigerantrather than liquid refrigerant may be provided to the compressor 60. Theaccumulator 72 may include a desiccant that absorbs small amounts ofwater moisture from the refrigerant. A second outlet 78D of internalheat exchanger 78 is directly coupled to inlet or suction side 60A ofcompressor 60.

An outlet side of second control valve 222 is directly coupled to aninlet of accumulator 72 and an outlet of battery chiller heat exchanger236. An outlet side of third expansion valve 274 is directly coupled toan inlet side of battery chiller heat exchanger 236. An outlet side ofbattery chiller heat exchanger 236 is directly coupled to an inlet sideof accumulator 72. Third expansion valve 274 may be a TXV with shutoff,a fixed area expansion device, or an electronic expansion valve (EXV).In this example, battery chiller expansion device 274 and expansiondevice 74 include shut-off valves for preventing flow through therespective valves.

Battery chiller loop 235 includes second electrical energy storagedevice 220, battery chiller pump 224, and battery chiller heat exchanger236. Heat from second electrical energy storage device 220 may berejected to refrigerant flowing through battery chiller heat exchanger236. Thus, coolant in battery chiller loop 235 is fluidically isolatedfrom refrigerant in heat pump subsystem 32.

The climate control system 24 may circulate air and/or control or modifythe temperature of air that is circulated in the passenger compartment20. The climate control system 24 may include a coolant subsystem 30, aheat pump subsystem 32, and a ventilation subsystem 34. Coolant incoolant subsystem is fluidically isolated from refrigerant in heat pumpsubsystem 32.

The coolant subsystem 30, which may also be referred to as a coolantloop, may circulate a fluid, such as coolant, to cool the engine 12 orelectric machine (not shown). For example, waste heat that is generatedby the engine 12 when the engine is running or operational may betransferred to the coolant and then circulated to one or more heatexchangers to transfer thermal energy from the coolant. In at least oneexample, the coolant subsystem 30 may include a coolant pump 40, anintermediate heat exchanger 42 that may be fluidly interconnected byconduits such as tubes, hoses, pipes, or the like. The coolant subsystem30 may also include a radiator (not shown) that may be disposed in theengine compartment 22 for transferring thermal energy to the ambient airsurrounding the vehicle 10.

The coolant pump 40 may circulate coolant through the coolant subsystem30. The coolant pump 40 may be powered by an electrical power source.The coolant pump 40 may receive coolant from the engine 12 and circulatethe coolant in a closed loop. For instance, when the climate controlsystem 24 is in a heating mode, coolant may be routed from the coolantpump 40 to the intermediate heat exchanger 42 and then to the heatercore 44 before returning to the engine 12 as represented by the arrowedlines 275.

The intermediate heat exchanger 42 may facilitate the transfer ofthermal energy between the coolant subsystem 30 and the heat pumpsubsystem 32. The intermediate heat exchanger 42 may be part of thecoolant subsystem 30 and the heat pump subsystem 32. The intermediateheat exchanger 42 may have any suitable configuration. For instance, theintermediate heat exchanger 42 may have a plate-fin, tube-fin, ortube-and-shell configuration that may facilitate the transfer of thermalenergy without mixing the heat transfer fluids in the coolant subsystem30 and heat pump subsystems 32. Heat may be transferred from the heatpump subsystem 32 to the coolant via the intermediate heat exchanger 42when the climate control system 24 is in a heating mode as will bediscussed in more detail below.

The heater core 44 may transfer thermal energy from the coolant to airin the passenger compartment 20. The heater core 44 may be disposed inthe passenger compartment 20 in the ventilation subsystem 34 and mayhave any suitable configuration. For example, the heater core 44 mayhave a plate-fin or tube-fin construction in one or more examples.

The heat pump subsystem 32 may transfer thermal energy to or from thepassenger compartment 20 and to the coolant subsystem 30. In at leastone example, the heat pump subsystem 32 may be configured as a vaporcompression heat pump subsystem in which a fluid is circulated throughthe heat pump subsystem 32 to transfer thermal energy to or from thepassenger compartment 20. The heat pump subsystem 32 may operate invarious modes, including, but not limited to a cooling mode and aheating mode. In the cooling mode, the heat pump subsystem 32 maycirculate a heat transfer fluid, which may be called a refrigerant, totransfer thermal energy from inside the passenger compartment 20 tooutside the passenger compartment 20.

The ventilation subsystem 34 may circulate air in the passengercompartment 20 of the vehicle 10. In addition, airflow through thehousing 90 and internal components is represented by the arrowed lines277.

Controller 212 includes executable instructions of the methods in FIGS.5-8 to operate the valves, fans, and pumps or compressors of the systemshown in FIGS. 2-4B. Controller 212 includes inputs 201 and outputs 202to interface with devices in the system of FIGS. 2-4B. Controller 212also includes a central processing unit 205 and non-transitory memory206 for executing the method of FIGS. 5-8.

Each of the devices shown in FIGS. 2-4B that are fluidically coupled viaconduits (e.g., solid lines) have an inlet and an outlet based on thedirection of flow direction arrows 204, 206, 302, 304, 402, 404, and406. Inlets of the devices are locations where the conduit enters thedevice in the direction of flow according to the flow direction arrows.Outlets of the devices are locations where the conduit exits the devicein the direction of flow according to the flow direction arrows.

The system of FIG. 2 may be operated in a cooling mode. In cooling mode,passenger compartment 20 may be cooled. The cooling mode is activated byopening fixed first control valve 262, opening the shut-off valve ofbattery chiller TXV 274 if battery chilling is desired, opening theshut-off valve of expansion device 74, closing second control valve 222,activating compressor 60, activating fan 92, and activating batterychiller pump 224 if desired.

During cooling mode, refrigerant flows through heat pump subsystem 32 inthe direction of arrows 204. Coolant flows in battery chiller loop 236in the direction indicated by arrows 206. Thus, in cooling mode,refrigerant exits compressor 60 and enters intermediate heat exchanger42. The refrigerant then moves through the first control valve 262,thereby reducing flow through expansion device 264, so that the pressureloss across expansion device 264 is small. Refrigerant travels from thefirst control valve 262 to the exterior heat exchanger 66 which operatesas a condenser. Condensed refrigerant then enters internal heatexchanger 78 where heat may be transferred from condensed refrigerantentering internal heat exchanger 78 from exterior heat exchanger 66 tovapor refrigerant entering internal heat exchanger from interior heatexchanger 76. The liquid refrigerant then enters expansion device 74 andbattery chiller TXV 274 where it expands to provide cooling to passengercompartment 20 and battery chiller loop 235. Heat is transferred fromcoolant circulating in battery chiller loop 235 to refrigerant in heatpump subsystem 32 via battery chiller heat exchanger 236. Likewise, heatis transferred from passenger compartment 20 to refrigerant in heat pumpsubsystem 32 via interior heat exchanger 76. The heated refrigerant isdirected to internal heat exchanger 78 before it is returned tocompressor 60 to be recirculated.

The ventilation subsystem 34 may circulate air in the passengercompartment 20 of the vehicle 10. The ventilation subsystem 34 may havea housing 90, a blower 92, and a temperature door 94. The housing 90 mayreceive components of the ventilation subsystem 34. In FIG. 2, thehousing 90 is illustrated such that internal components are visiblerather than hidden for clarity. In addition, airflow through the housing90 and internal components is represented by the arrowed lines 277. Thehousing 90 may be at least partially disposed in the passengercompartment 20. For example, the housing 90 or a portion thereof may bedisposed under an instrument panel of the vehicle 10. The housing 90 mayhave an air intake portion 100 that may receive air from outside thevehicle 10 and/or air from inside the passenger compartment 20. Forexample, the air intake portion 100 may receive ambient air from outsidethe vehicle 10 via an intake passage, duct, or opening that may belocated in any suitable location, such as proximate a cowl, wheel well,or other vehicle body panel. The air intake portion 100 may also receiveair from inside the passenger compartment 20 and recirculate such airthrough the ventilation subsystem 34. One or more doors or louvers maybe provided to permit or inhibit air recirculation.

The blower 92 may be disposed in the housing 90. The blower 92, whichmay also be called a blower fan, may be disposed near the air intakeportion 100 and may be configured as a centrifugal fan that maycirculate air through the ventilation subsystem 34.

The temperature door 94 may be disposed between the interior heatexchanger 76 and the heater core 44. In the example shown, thetemperature door 94 is disposed downstream of the interior heatexchanger 76 and upstream of the heater core 44. The temperature door 94may block or permit airflow through the heater core 44 to help controlthe temperature of air in the passenger compartment 20. For instance,the temperature door 94 may permit airflow through the heater core 44 inthe heating mode such that heat may be transferred from the coolant toair passing through the heater core 44. This heated air may then beprovided to a plenum for distribution to ducts and vents or outletslocated in the passenger compartment 20. The temperature door 94 maymove between a plurality of positions to provide air having a desiredtemperature. In FIG. 2, the temperature door 94 is shown in a full heatposition in which airflow is directed through the heater core 44.

Temperature sensor 250 senses refrigerant temperature at outlet side 66Bof exterior heat exchanger 66. Temperature sensor 250 may be located ona fin or tube of exterior heat exchanger 66. Alternatively, temperaturesensor 250 may be located in a flow path of refrigerant in exterior heatexchanger 66. Pressure sensor 251 senses refrigerant pressure at outletside 60B of compressor 60. Optional pressure sensor 252 sensesrefrigerant pressure at inlet side or suction side 60A of compressor 60.Pressure sensor 253 senses refrigerant pressure at an outlet side ofbattery chiller heat exchanger 236. Optional pressure sensor 254 sensesrefrigerant pressure at an inlet side of accumulator 72. Temperaturesensor 255 senses refrigerant temperature an outlet side of interiorheat exchanger 76. Temperature sensor 255 may be located on a fin ortube of interior heat exchanger 76. Alternatively, temperature sensor255 may be located in a flow path of refrigerant in interior heatexchanger 76. Signals from temperature and pressure sensors 250-255 areinput to controller 212.

Components of the system shown in FIGS. 3-4B having the same numericallabels shown in FIG. 2 are the same as components described in thesystem of FIG. 2. Further, the components or devices operate the same asdescribed in FIG. 2 unless otherwise described. For example, exteriorheat exchanger 66 shown in FIG. 2 and exterior heat exchanger 66 shownin FIG. 3 have the same numerical label 66.

Referring now to FIG. 3, climate control system 24 is the same asclimate control system 24 shown in FIG. 2; however, FIG. 3 shows climatecontrol system 24 operating in a heating mode. In heating mode,passenger compartment 20 may be warmed. The heating mode is activated byclosing first control valve 262, closing the shut-off valve of batterychiller TXV 274, closing the shut-off valve of expansion device 74,opening second control valve 222, activating compressor 60, activatingfan 92, and activating coolant pump 40. During heating mode, refrigerantflows through heat pump subsystem 32 (e.g., refrigerant loop) in thedirection of arrows 304. Coolant flows in coolant subsystem 30 in thedirection indicated by arrows 302.

In heating mode, refrigerant exits compressor 60 and enters intermediateheat exchanger 42 which operates as a condenser. Heat is transferredfrom refrigerant to coolant in coolant subsystem 30 via intermediateheat exchanger 42. Coolant circulating in coolant subsystem 30 is heatedat intermediate heat exchanger 42 before it enters heater core 44 wherepassenger compartment air extracts heat from the circulating coolant.Coolant is then returned to coolant pump 40 to be recirculated.

The refrigerant exits intermediate heat exchanger 42 and moves throughfixed area expansion device 264, and not first control valve 262, sothat refrigerant expansion occurs. Refrigerant travels from the fixedarea expansion device 264 to the exterior heat exchanger 66 whichoperates as an evaporator. Refrigerant exits exterior heat exchanger 66and passes through second control valve 222. The refrigerant then passesthrough an inlet of accumulator 72 before entering input 78C of internalheat exchanger 78 before returning to compressor 60. Compressor 60increases refrigerant temperature and pressure. Refrigerant does notflow through interior heat exchanger 76 and battery chiller heatexchanger 236 in heating mode.

Referring now to FIG. 4A, climate control system 24 is the same asclimate control system 24 shown in FIG. 2; however, FIG. 4A showsclimate control system 24 operating in a first dehumidification mode.For the sake of brevity, the description of FIG. 2 applies except forthe differences described hereafter. The first dehumidification modeprovides for removing moisture from passenger compartment air andreheating the air. The first dehumidification mode is activated byclosing first control valve 262, optionally opening the shut-off valveof battery chiller expansion device 274, opening the shut-off valve ofexpansion device 74, closing second control valve 222, activatingcompressor 60, activating fan 92, activating coolant pump 40, andactivating battery chiller pump 224 if desired.

During the first dehumidification mode, refrigerant flows through heatpump subsystem 32 in the direction of arrows 404. Passing refrigerantthrough expansion device 264 and exterior heat exchanger 66 changes therefrigerant state from all vapor to a variable mixture of vapor andliquid before the refrigerant passes through internal heat exchanger 78and interior heat exchanger 76. Coolant flows in coolant subsystem 30 inthe direction indicated by arrows 402.

Activating coolant pump 40 allows heat to be transferred fromrefrigerant in heat pump subsystem 32 to coolant in coolant subsystem 40via intermediate heat exchanger 42. At least a portion of heat extractedfrom passenger compartment 20 via interior heat exchanger 76 may bereturned to passenger compartment 20 via heater core 44. Moisture inpassenger compartment air may be extracted by first cooling passengercompartment air at interior heat exchanger 76. The moisture reducedpassenger compartment air may then be heated via heater core 44 to warmthe passenger compartment or defog vehicle windows.

Referring now to FIG. 4B, climate control system 24 is the same asclimate control system 24 shown in FIG. 2; however, FIG. 4B showsclimate control system 24 operating in a second dehumidification mode.The second dehumidification mode also provides for removing moisturefrom passenger compartment air and reheating the air. The seconddehumidification mode is activated by opening first control valve 262,optionally opening the shut-off valve of battery chiller expansiondevice 274, opening the shut-off valve of expansion device 74, closingsecond control valve 222, activating compressor 60, activating fan 92,activating coolant pump 40, and activating battery chiller pump 224 ifdesired.

During the second dehumidification mode, refrigerant flows through heatpump subsystem 32 in the direction of arrows 499. A large portion ofrefrigerant by-passes expansion device 264 and enters exterior heatexchanger 66 when first control valve 262 is open. Consequently, therefrigerant changes state from vapor to liquid before reaching expansiondevice 74. Coolant flows in coolant subsystem 30 in the directionindicated by arrows 402. Coolant may flow through battery chiller loop235 in the direction of arrows 406.

Activating coolant pump 40 allows heat to be transferred fromrefrigerant in heat pump subsystem 32 to coolant in coolant subsystem 40via intermediate heat exchanger 42. At least a portion of heat extractedfrom passenger compartment 20 via interior heat exchanger 76 may bereturned to passenger compartment 20 via heater core 44. Moisture inpassenger compartment air may be extracted by first cooling passengercompartment air at interior heat exchanger 76. The moisture reducedpassenger compartment air may then be heated via heater core 44 to warmthe passenger compartment or defog vehicle windows.

Thus, the system of FIGS. 1-4B provides for a vehicle system,comprising: a refrigerant loop including a compressor; a first pressuresensor; and a controller including executable instructions stored innon-transitory memory to adjust a speed of the compressor in response toa pressure ratio across an outlet of the compressor and an inlet of thecompressor, the pressure ratio based at least in part on output of thefirst pressure sensor. The vehicle system includes where the firstpressure sensor is positioned to sense outlet pressure of thecompressor. The vehicle system further comprises additional instructionsto estimate a pressure at the inlet of the compressor.

In some examples, the vehicle system includes where the pressure at theinlet of the compressor is based on a pressure at an outlet of a batterychiller heat exchanger. The vehicle system includes where the pressureat the inlet of the compressor is based on a pressure at an outlet of anexterior heat exchanger. The vehicle system includes where the pressureat the inlet of the compressor is based on a pressure at an outlet of avehicle passenger cabin heat exchanger or interior heat exchanger. Thevehicle system further comprises additional instructions to adjust thespeed of the compressor responsive to a compressor pressure ratiocontrol mode proportional/integral controller that adjusts the speed ofthe compressor only when a compressor pressure ratio exceeds a thresholdpressure ratio.

In a first example, the system also provides for a vehicle system,comprising: a refrigerant loop including a compressor; a first pressuresensor; and a controller including executable instructions stored innon-transitory memory to adjust a speed of the compressor in a firstmode in response to a pressure ratio across an outlet of the compressorand an inlet of the compressor, and to adjust the speed of thecompressor in a second mode response to a pressure at the outlet of thecompressor and not a pressure at the inlet of the compressor. In asecond example, the vehicle system includes where the pressure ratio isbased at least in part on output of the first pressure sensor.

In some examples, the vehicle system further comprises a second pressuresensor positioned at the inlet of the compressor, and further comprisingbasing the pressure ratio on the second pressure sensor positioned atthe inlet of the compressor. The vehicle system further comprisesadditional instructions to adjust the speed of the compressor responsiveto a proportional/integral controller that adjusts the speed of thecompressor only when a pressure at the outlet of the compressor exceedsa threshold pressure. The vehicle system includes where the first modeis activated in response to operating a heat pump that includes therefrigerant loop in a heating mode. The vehicle system includes wherethe second mode is activated in response to operating a heat pump thatincludes the refrigerant loop in a cooling mode. The vehicle systemincludes where the first mode is activated in response to operating aheat pump that includes the refrigerant loop in a dehumidification mode.

Referring now to FIG. 5, a method for operating a climate control systemis shown. The method of FIG. 5 may provide the climate control systemmodes described in FIGS. 2-4B. Further, at least portions of the methodof FIG. 5 may be included in the system of FIGS. 2-4B as executableinstructions stored in non-transitory memory. Further still, portions ofthe method of FIG. 5 may be actions taken in the physical world by acontroller in cooperation with the methods of FIGS. 6-9.

At 502, method 500 judges if the climate control system heat pump isactivated. Method 500 may judge that the heat pump is activated based oninput from a driver to a controller. If method 500 judges that the heatpump is activated, the answer is yes and method 500 proceeds to 504.Otherwise, the answer is no and method 500 proceeds to 520.

At 520, method 500 deactivates the heat pump compressor. Further, powermay be removed from the various expansion valve bypass valves andshut-off valves within the expansion valves so that the climate controlsystem enters a default mode, such as heating mode. Alternatively, thevarious expansion valve bypass valves and shut-off valves within theexpansion devices may be held in their present states. Method 500proceeds to exit after the compressor and valves have been deactivated.The compressor speed is zero when the compressor is deactivated.

At 504, method 500 judges if the climate control system's exterior oroutside heat exchanger (OHX) 66 or exterior heat exchanger is operatingas an evaporator. The OHX operates as an evaporator in heating mode andthe first dehumidification mode. The OHX operates as a condenser incooling mode and the second dehumidification mode. If method 500 judgesthat the heat pump is in heating mode or the first dehumidificationmode, the OHX is operating as an evaporator and method 500 proceeds to508. If method 500 judges that the OHX is not operating as anevaporator, such as during cooling mode where the OHX operates as acondenser, method 500 proceeds to 512.

At 508, method 500 judges if a pressure at an outlet side of the heatpump compressor (P_(cp) _(_) _(dis)), or head pressure, is greater thana system maximum threshold pressure. In one example, pressure at theoutlet side of the heat pump compressor may be determined via a pressuresensor. If so, the answer is yes and method 500 proceeds to 512.Otherwise, the answer is no and method 500 proceeds to 510.

At 512, method 500 adjusts heat pump compressor speed responsive to headpressure or outlet pressure of the heat pump compressor. By adjustingcompressor speed responsive to heat pump compressor outlet pressure, thesystem controls the condensing pressure when the exterior heat exchangeris operating as a condenser. Further, adjusting compressor speedresponsive to compressor head pressure provides for limiting headpressure whether the pressure ratio across the pump is large or small sothat desirable system pressures may not be exceeded.

Compressor speed control based on compressor head pressure may beperformed via two proportional/integral (PI) controllers. A first PIcontroller is a temperature controller that controls compressor speed inresponse to a temperature in the heat pump system. For example, incooling or dehumidification mode, compressor speed may be adjustedresponsive to a temperature at an outlet side of an evaporator (e.g.,exterior heat exchanger). In heating mode, the compressor speed may beadjusted responsive to heater core temperature. If compressor headpressure is greater than a threshold pressure (e.g., a system pressurelimit), a second PI controller is activated. The second PI controllermay adjust compressor speed to reduce compressor head pressure.

In one example during heat pump cooling mode, compressor speed isadjusted via a head pressure proportional/integral controller.Specifically, compressor speed is adjusted responsive to compressor headpressure and evaporator or refrigerant temperature. An actual evaporatoror refrigerant temperature is subtracted from a desired evaporatortemperature to provide an evaporator temperature error. The evaporatortemperature error is multiplied by evaporator temperature proportionaland integral gains in a first loop of the compressor controller toprovide a first compressor speed adjustment. An actual compressor outletpressure is subtracted from a head pressure limit to provide a headpressure error value. If the head pressure error value is negative, itis multiplied by head pressure proportional and integral gains toprovide a second compressor speed adjustment. The head pressureproportional and integral gains have more control authority than theevaporator temperature proportional and integral gains. The first andsecond compressor speed adjustments are added and compressor speed isadjusted based on the result. Method 500 proceeds to exit after heatpump compressor speed is adjusted.

At 510, method 500 adjusts heat pump compressor speed in response to apressure ratio between an outlet of the heat pump compressor and aninlet of the heat pump compressor. In one example, the heat pumpcompressor speed is controlled according to the method of FIG. 9 (e.g.,a third PI controller). The pressure at the heat pump compressor inletmay be measured or estimated according to one of the methods describedin FIGS. 6-8. Method 500 adjusts speed of the heat pump compressorresponsive to the pressure ratio between the outlet of the heat pumpcompressor and the inlet of the heat pump compressor because pressure atthe heat pump inlet may vary widely when the OHX operates as anevaporator. If the pressure ratio is too high, compressor lubricationmay be limited, thereby resulting in compressor degradation. Byadjusting compressor speed responsive to the heat pump pressure ratio,the possibility of operating the compressor at low flow conditions maybe reduced. Larger heat pump pressure ratios may result from evaporatoroutlet pressures that are driven by exterior ambient temperatures. Thus,it may be desirable to control heat pump compressor speed responsive tothe pressure ratio instead of compressor head pressure during conditionswhere the exterior heat exchanger is operating as an evaporator. Method500 proceeds to exit after compressor speed is adjusted.

In this way, the heat pump compressor speed may be adjusted based on aratio of compressor head pressure and compressor inlet pressure whencompressor inlet pressure may vary widely due to the OHX operating as anevaporator.

Referring now to FIG. 6, a method for inferring heat pump compressorinlet pressure is shown. The method of FIG. 6 may operate in concertwith the methods of FIGS. 5 and 9 in the system of FIGS. 1-4B. Further,portions of method 600 may be incorporated to a controller as executableinstructions stored in non-transitory memory while other portions of themethod of FIG. 6 may be physical actions taken in the physical world viaa controller. The method of FIG. 6 may be activated when the heat pumpoperates in a heating mode.

At 602, method 600 determines pressure at an outlet of a battery chillerheat exchanger. The battery chiller heat exchanger may be positioned inthe climate control system as is shown in FIGS. 2-4B. In one example, apressure sensor is positioned at an outlet of the battery chiller heatexchanger and the pressure sensor supplies a signal to a controller thatdetermines pressure at the outlet of the battery chiller heat exchangerbased on the signal. Method 600 proceeds to 604 after pressure at thebattery chiller heat exchanger outlet is determined.

At 604, method 600 determines compressor speed. Compressor speed may bedetermined via a speed sensor or it may be inferred via voltage andcurrent supplied to operate compressor 60. Method 600 proceeds to 606after compressor speed is determined.

At 606, method 600 determines an accumulator inlet pressure correction.In one example, the accumulator is positioned in the climate controlsystem 24 as shown in FIGS. 2-4B. The pressure correction between thebattery chiller outlet and the accumulator inlet is based on heat pumpcompressor speed. In particular, a table of empirically determinedpressure correction values based on compressor speed is indexed bycompressor speed and the table outputs a pressure correction value.Method 600 proceeds to 608 after the accumulator inlet pressurecorrection is determined.

At 608, method 600 determines accumulator inlet pressure. In oneexample, the accumulator inlet pressure is based on battery chiller heatexchanger outlet pressure. In particular, the accumulator inlet pressureis determined by subtracting the correction determined at 606 from thebattery chiller outlet pressure determined at 602. Method 600 proceedsto 610 after the accumulator inlet pressure is determined.

At 610, method 600 determines a heat pump compressor inlet pressure orsuction pressure correction. In one example, the heat pump compressor 60is positioned in the climate control system 24 as shown in FIGS. 2-4B.The pressure correction between the accumulator inlet and the heat pumpcompressor inlet is based on heat pump compressor speed. In particular,a table of empirically determined pressure correction values based oncompressor speed is indexed by compressor speed and the table outputs apressure correction value for the heat pump compressor inlet. Method 600proceeds to 612 after the heat pump compressor inlet pressure correctionis determined.

At 612, method 600 determines heat pump compressor inlet pressure. Inone example, the heat pump compressor inlet pressure is based on theaccumulator inlet pressure and the heat pump compressor inlet pressurecorrection. In particular, the heat pump compressor inlet pressurecorrection is subtracted from the accumulator inlet pressure determinedat 608 to determine the heat pump compressor inlet pressure. Method 600proceeds to 614 after the heat pump compressor inlet pressure isdetermined.

At 614, method 600 determines outlet pressure at an outlet of the heatpump compressor. In one example, a pressure sensor is positioned at theheat pump compressor outlet and the pressure sensor supplies a signal toa controller that determines pressure at the heat pump compressor outletbased on the signal. Method 600 proceeds to 616 after pressure at theheat pump compressor outlet is determined.

At 616, method 600 determines a heat pump compressor pressure ratio. Theheat pump compressor pressure ratio is determined by dividing the heatpump compressor outlet pressure determined at 614 by the compensatedheat pump compressor inlet pressure determined at 612. Method 600proceeds to 618 after the heat pump compressor pressure ratio isdetermined.

At 618, method 600 determines a heat pump compressor speed adjustmentfrom the heat pump pressure ratio. The compressor speed may bedetermined as is described in FIGS. 5 and 9. Method 600 proceeds to 620after the heat pump compressor speed adjustment is determined.

At 620, method 600 adjusts the heat pump compressor speed. The heat pumpcompressor speed may be increased via adjusting a voltage frequencyand/or increasing an amount of electrical current and/or voltagesupplied to the heat pump compressor via a controller. The heat pumpcompressor speed may be decreased via reducing a voltage frequencyand/or decreasing an amount of electrical current or voltage supplied tothe heat pump compressor via a controller. Further, the heat pumpcompressor speed may be closed-loop controlled based on a measured heatpump compressor speed. Method 600 proceeds to exit after heat pumpcompressor speed is adjusted.

In this way, the heat pump compressor pressure ratio may be estimatedbased on battery chiller outlet pressure. If the pressure ratio isgreater than is desired, the compressor speed may be reduced to increaserefrigerant and lubricant flow through the heat pump compressor.

Referring now to FIG. 7, a method for inferring heat pump compressorinlet pressure is shown. The method of FIG. 7 may operate in concertwith the methods of FIGS. 5 and 9 in the system of FIGS. 1-4B. Further,portions of method 700 may incorporated to a controller as executableinstructions stored in non-transitory memory while other portions of themethod of FIG. 7 may be physical actions taken in the physical world viaa controller. The method of FIG. 7 may be activated when the heat pumpoperates in a heating mode and does not include a battery chiller heatexchanger.

At 702, method 700 determines temperature at an outlet of the OHX andestimates pressure at the OHX outlet based on temperature at the outletof the OHX. The OHX may be positioned in the climate control system asis shown in FIGS. 2-4B. In one example, a temperature sensor ispositioned at an outlet of the OHX and the temperature sensor supplies asignal to a controller that determines temperature at the outlet of theOHX based on the signal. The temperature at the outlet of the OHX isused to index a table of thermodynamic property based saturationpressures at the outlet of the OHX. The saturation pressures are anestimate of pressure at the outlet of the OHX. Method 700 proceeds to704 after temperature and pressure at the OHX outlet is determined.

At 704, method 700 determines compressor speed. Compressor speed may bedetermined via a speed sensor or it may be inferred via voltage andcurrent supplied to operate compressor 60. Method 700 proceeds to 706after compressor speed is determined.

At 706, method 700 determines an accumulator inlet pressure correction.The pressure correction between the OHX outlet and the accumulator inletis based on heat pump compressor speed. In particular, a table ofempirically determined pressure correction values based on compressorspeed is indexed by compressor speed and the table outputs a pressurecorrection value. Method 700 proceeds to 708 after the accumulator inletpressure correction is determined.

At 708, method 700 determines accumulator inlet pressure. In oneexample, the accumulator inlet pressure is based on OHX outlet pressuredetermined at 702 and the accumulator inlet pressure correctiondetermined at 706. In particular, the accumulator inlet pressurecorrection determined at 706 is subtracted from the OHX outlet pressuredetermined at 702 to determine the accumulator inlet pressure. Method700 proceeds to 710 after the accumulator inlet pressure is determined.

At 710, method 700 determines a heat pump compressor inlet pressure orsuction pressure correction. The pressure correction between theaccumulator inlet and the heat pump compressor inlet accumulator inputis based on heat pump compressor speed. In particular, a table ofempirically determined pressure correction values based on compressorspeed is indexed by compressor speed and the table outputs a pressurecorrection value for the heat pump compressor inlet. Method 700 proceedsto 712 after the heat pump compressor inlet pressure correction isdetermined.

At 712, method 700 determines heat pump compressor inlet pressure. Inone example, the heat pump compressor inlet pressure is determined bysubtracting the heat pump compressor inlet compressor correctiondetermined a 710 from the accumulator inlet pressure determined at 708.Method 700 proceeds to 714 after the heat pump compressor inlet pressureis determined.

At 714, method 700 determines outlet pressure at an outlet of the heatpump compressor. In one example, a pressure sensor is positioned at theheat pump compressor outlet and the pressure sensor supplies a signal toa controller that determines pressure at the heat pump compressor outletbased on the signal. Method 700 proceeds to 716 after pressure at theheat pump compressor outlet is determined.

At 716, method 700 determines a heat pump compressor pressure ratio. Theheat pump compressor pressure ratio is determined by dividing the heatpump compressor outlet pressure determined at 714 by the compensatedheat pump compressor inlet pressure determined at 712. Method 700proceeds to 718 after the heat pump compressor pressure ratio isdetermined.

At 718, method 700 determines a heat pump compressor speed adjustmentfrom the heat pump pressure ratio. The compressor speed may bedetermined as is described in FIGS. 5 and 9. Method 700 proceeds to 720after the heat pump compressor speed adjustment is determined.

At 720, method 700 adjusts the heat pump compressor speed. The heat pumpcompressor speed may be increased via increasing a frequency of avoltage and/or increasing an amount of electrical current or voltagesupplied to the heat pump compressor via a controller. The heat pumpcompressor speed may be decreased via decreasing a frequency of avoltage and/or decreasing an amount of electrical current or voltagesupplied to the heat pump compressor via a controller. Further, the heatpump compressor speed may be closed-loop controlled based on a measuredheat pump compressor speed. Method 700 proceeds to exit after heat pumpcompressor speed is adjusted.

In this way, the heat pump compressor pressure ratio may be estimatedbased on OHX outlet temperature. If the pressure ratio is greater thanis desired, the compressor speed may be reduced to increase refrigerantflow and lubricant flow through the heat pump compressor.

Referring now to FIG. 8, a method for inferring heat pump compressorinlet pressure is shown. The method of FIG. 8 may operate in concertwith the methods of FIGS. 5 and 9 in the system of FIGS. 1-4B. Further,portions of method 800 may incorporated to a controller as executableinstructions stored in non-transitory memory while other portions of themethod of FIG. 8 may be physical actions taken in the physical world viaa controller. The method of FIG. 8 may be activated when the heat pumpoperates in a dehumidification mode.

At 802, method 800 determines temperature at an outlet of the interiorheat exchange 76 and estimates pressure at the interior heat exchangeroutlet based on temperature at the outlet of the interior heatexchanger. In one example, a temperature sensor is positioned at anoutlet of the interior heat exchanger and the temperature sensorsupplies a signal to a controller that determines temperature at theoutlet of the interior heat exchanger based on the signal. Thetemperature sensor may be in thermal communication with a fin or tube ofthe interior heat exchanger. Alternatively, the temperature sensor maybe positioned in a flow path of refrigerant. The temperature at theoutlet of the interior heat exchanger is used to index a table ofthermodynamic property based saturation pressures at the outlet of theinterior heat exchanger. The saturation pressures are an estimate ofpressure at the outlet of the interior heat exchanger. Method 800proceeds to 804 after temperature and pressure at the interior heatexchanger outlet is determined.

At 804, method 800 determines compressor speed. Compressor speed may bedetermined via a speed sensor or it may be inferred via voltage andcurrent supplied to operate compressor 60. Method 800 proceeds to 806after compressor speed is determined.

At 806, method 800 determines an accumulator inlet pressure correction.The pressure correction between the interior heat exchanger outlet andthe accumulator inlet is based on heat pump compressor speed. Inparticular, a table of empirically determined pressure correction valuesbased on compressor speed is indexed by compressor speed and the tableoutputs a pressure correction value. Method 800 proceeds to 808 afterthe accumulator inlet pressure correction is determined.

At 808, method 800 determines accumulator inlet pressure. In oneexample, the accumulator inlet pressure is determined by subtracting theaccumulator inlet pressure correction determined at 806 from theinterior heat exchanger outlet pressure determined at 802. Method 800proceeds to 810 after the accumulator inlet pressure is determined.

At 810, method 800 determines a heat pump compressor inlet pressure orsuction pressure correction. In one example, the heat pump compressor 60is positioned in the climate control system 24 as shown in FIGS. 2-4B.The pressure correction between the accumulator inlet and the heat pumpcompressor inlet accumulator input is based on heat pump compressorspeed. In particular, a table of empirically determined pressurecorrection values based on compressor speed is indexed by compressorspeed and the table outputs a pressure correction value for the heatpump compressor inlet. Method 800 proceeds to 812 after the heat pumpcompressor inlet pressure correction is determined.

At 812, method 800 determines heat pump compressor inlet pressure. Inone example, the heat pump compressor inlet pressure is determined bysubtracting the heat pump compressor inlet pressure correction from theaccumulator inlet pressure determined at 808. Method 800 proceeds to 814after the heat pump compressor inlet pressure is determined.

At 814, method 800 determines outlet pressure at an outlet of the heatpump compressor. In one example, a pressure sensor is positioned at theheat pump compressor outlet and the pressure sensor supplies a signal toa controller that determines pressure at the heat pump compressor outletbased on the signal. Method 800 proceeds to 816 after pressure at theheat pump compressor outlet is determined.

At 816, method 800 determines a heat pump compressor pressure ratio. Theheat pump compressor pressure ratio is determined by dividing the heatpump compressor outlet pressure determined at 814 by the compensatedheat pump compressor inlet pressure determined at 812. Method 800proceeds to 818 after the heat pump compressor pressure ratio isdetermined.

At 818, method 800 determines a heat pump compressor speed adjustmentfrom the heat pump pressure ratio. The compressor speed may bedetermined as is described in FIGS. 5 and 9. Method 800 proceeds to 820after the heat pump compressor speed adjustment is determined.

At 820, method 800 adjusts the heat pump compressor speed. The heat pumpcompressor speed may be increased via increasing a voltage frequencyand/or increasing an amount of electrical current or voltage supplied tothe heat pump compressor via a controller. The heat pump compressorspeed may be decreased via decreasing a voltage frequency and/ordecreasing an amount of electrical current or voltage supplied to theheat pump compressor via a controller. Further, the heat pump compressorspeed may be closed-loop controlled based on a measured heat pumpcompressor speed. Method 800 proceeds to exit after heat pump compressorspeed is adjusted.

In this way, the heat pump compressor pressure ratio may be estimatedbased on interior heat exchanger outlet temperature. If the pressureratio is greater than is desired, the compressor speed may be reduced toincrease refrigerant and lubricant flow through the heat pumpcompressor.

Referring now to FIG. 9, a method for adjusting heat pump compressorspeed responsive to heat pump compressor pressure ratio is shown. Themethod of FIG. 9 may operate in cooperation with the methods of FIGS.5-8 to operate a heat pump compressor. At least portions of the methodof FIG. 9 may be included as executable instructions stored innon-transitory memory of the system shown in FIGS. 1-4B. Further,portions of the method of FIG. 9 may be performed in the physical worldto transform operating states of one or more devices.

At 902, method 900 determines a pressure ratio across a heat pumpcompressor. In one example, pressure sensors may sense inlet and outletpressures of the heat pump compressor. In other examples, heat pumpcompressor outlet pressure may be determined via a pressure sensor andheat pump compressor inlet pressure may be estimated as described inFIGS. 6-8. The pressure ratio may be determined via dividing the heatpump outlet pressure by the heat pump inlet pressure. Method 900proceeds to 904 after the heat pump compressor ratio is determined.

At 904, method 900 judges if the heat pump compressor ratio is greaterthan a threshold. The threshold pressure ratio may be empiricallydetermined and stored to memory. If method 900 judges that the heat pumpcompressor ratio is greater than the threshold, the answer is yes andmethod 900 proceeds to 806. Otherwise, the answer is no and method 900proceeds to 910.

At 910, method 900 provides a heat pump compressor speed adjustmentvalue of zero so that heat pump compressor speed is not adjustedresponsive to the heat pump compressor pressure ratio. For example, atlower pressure ratios (e.g., 10:1) it may be expected that refrigerantand lubricant flow through the compressor is sufficient to lubricate theheat pump compressor. Therefore, compressor speed is not adjusted andthe adjustment value is zero. However, at higher pressure ratios (e.g.,20:1) it may be expected that refrigerant and lubricant flow though thecompressor is less than is desired. Therefore, the compressor speed isadjusted to a lower speed so that the heat pump compressor may operateat a speed where lubricant flow at the present heat pump compressorpressure ratio may be sufficient to reduce the possibility of heat pumpcompressor degradation. Method 900 proceeds to exit after the heat pumpcompressor speed is not adjusted.

At 906, method 900 determines a heat pump compressor pressure ratioerror. In one example, the heat pump compressor pressure ratiodetermined at 902 is subtracted from a desired heat pump compressorpressure ratio that may be empirically determined. The result is theheat pump compressor pressure ratio error. Method 900 proceeds to 908after the heat pump compressor pressure ratio error is determined.

At 908, method 900 operates on the heat pump compressor pressure ratioerror with a proportional/integral controller. Thus, method 900 providesa heat pump compressor pressure ratio proportional/integral controllerthat has different proportional and integral gains than the compressorhead pressure proportional/integral controller described at 512. Theproportional and integral gains may be empirically determined and storedin controller memory. The proportional controller may be described viathe following equations:Speed_adj=(P·e)+(Iterm)Iterm=(I·e·t)+Iterm_prevwhere Speed_adj is the heat pump compressor speed adjustment, P is aproportional gain, e is the heat pump compressor pressure ratio error,Iterm is the integral correction, I is the integral gain, Iterm_prev isthe previous value of the integral correction, and t is the controllerloop time.

The heat pump compressor speed is adjusted to a new value based on thevalue of Speed_adj. The compressor speed may be decreased if thepressure ratio increases (e.g., increases from 15:1 to 18:1). The heatpump compressor speed is adjusted via adjusting voltage and currentsupplied to the heat pump compressor. Method 900 proceeds to exit afterheat pump compressor speed is adjusted.

Thus, the methods of FIGS. 5-9 provide for a vehicle climate controlmethod, comprising: inferring a pressure at an inlet of a heat pumpcompressor from a pressure at an outlet of a heat exchanger via acontroller; and adjusting speed of a heat pump compressor in response toa pressure ratio across the heat pump compressor via a controller, thepressure ratio based on the inferred pressure at the inlet of the heatpump compressor. The vehicle climate control method includes where theheat exchanger is a battery chiller heat exchanger. The vehicle climatecontrol method includes where the heat exchanger is a vehicle cabin orinterior heat exchanger. The vehicle climate control method includeswhere the heat exchanger is an exterior heat exchanger. The vehicleclimate control method further comprises adjusting speed of the heatpump compressor in response to output of a proportional/integralcontroller that provides an output only when pressure at an outlet ofthe heat pump compressor is greater than a threshold pressure. Thevehicle climate control method includes where the inferring of thepressure at the inlet of the heat pump occurs when a heat pump isoperated in a heating mode or a dehumidification mode.

As will be appreciated by one of ordinary skill in the art, methodsdescribed in FIG. 6 may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various steps orfunctions illustrated may be performed in the sequence illustrated, inparallel, or in some cases omitted. Likewise, the order of processing isnot necessarily required to achieve the objects, features, andadvantages described herein, but is provided for ease of illustrationand description. Although not explicitly illustrated, one of ordinaryskill in the art will recognize that one or more of the illustratedsteps or functions may be repeatedly performed depending on theparticular strategy being used. Further, the methods described hereinmay be a combination of actions taken by a controller in the physicalworld and instructions within the controller. At least portions of thecontrol methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other system hardware.

This concludes the description. The reading of it by those skilled inthe art would bring to mind many alterations and modifications withoutdeparting from the spirit and the scope of the description. For example,the systems and methods described herein may be applied to full electricvehicles and vehicles that include an engine and an electric motor forpropulsion.

The invention claimed is:
 1. A vehicle climate control method,comprising: via a controller, inferring a pressure at an inlet of a heatpump compressor from a suction pressure correction and a pressure at anoutlet of a battery chiller heat exchanger including subtracting anaccumulator inlet compensation pressure from the pressure at the outletof the battery chiller heat exchanger, and where the accumulator inletcompensation pressure is based on a speed of the heat pump compressor;adjusting the speed of the heat pump compressor in response to apressure ratio across the heat pump compressor via the controller in afirst mode while an outside heat exchanger is operating as anevaporator, the pressure ratio based on the inferred pressure at theinlet of the heat pump compressor.
 2. The vehicle climate control methodof claim 1, further comprising subtracting a heat pump compressor inletpressure correction from an accumulator inlet pressure to infer thepressure at the inlet of the heat pump compressor.
 3. The vehicleclimate control method of claim 2, where the heat pump compressor inletpressure correction is based on the speed of the heat pump compressor.4. The vehicle climate control method of claim 1, further comprisingheating a passenger compartment of a vehicle via a refrigerant thatheats coolant circulating in a coolant loop that includes an engine, therefrigerant included in a refrigerant loop that includes the heat pumpcompressor.
 5. The vehicle climate control method of claim 1, furthercomprising providing a heat pump compressor speed adjustment in responseto output of a proportional and integral controller when the heat pumpcompressor pressure ratio is greater than a threshold pressure ratio,and not providing the heat pump compressor speed adjustment in responseto output of the proportional and integral controller when the heat pumppressure ratio is less than the threshold pressure ratio.
 6. The vehicleclimate control method of claim 1, where the inferring of the pressureat the inlet of the heat pump compressor occurs when a heat pump thatincludes the heat pump compressor is operated in a heating mode or adehumidification mode.
 7. The vehicle climate control method of claim 1,further comprising adjusting the speed of the heat pump compressor in asecond mode via the controller responsive to a pressure at an outlet ofthe heat pump compressor and not the pressure at the inlet of the heatpump compressor.
 8. The vehicle climate control method of claim 7, whereadjusting speed of the heat pump compressor includes adjusting the heatpump compressor speed via two proportional and integral controllers. 9.The vehicle climate control method of claim 8, where a first of the twoproportional and integral controllers adjusts the speed of the heat pumpcompressor responsive to a temperature and where a second of the twoproportional and integral controllers adjusts the speed of the heat pumpcompressor to reduce head pressure of the heat pump compressor.
 10. Avehicle climate control method, comprising: via a controller, inferringa pressure at an inlet of a heat pump compressor from a pressure at anoutlet of an exterior heat exchanger including subtracting anaccumulator compensation pressure from the pressure at the outlet of theexterior heat exchanger to determine an accumulator inlet pressure,where the accumulator compensation pressure is based on a speed of theheat pump compressor, and subtracting a pressure correction for theinlet of the heat pump compressor from the accumulator inlet pressure;and adjusting the speed of the heat pump compressor in response to apressure ratio across the heat pump compressor via the controller whilethe exterior heat exchanger is operating as an evaporator, the pressureratio based on the inferred pressure at the inlet of the heat pumpcompressor.
 11. The vehicle climate control method of claim 10, furthercomprising heating a passenger compartment of a vehicle via arefrigerant that heats coolant circulating in a coolant loop thatincludes an engine, the refrigerant included in a refrigerant loop thatincludes the heat pump compressor.